We propose to examine three aspects of visual functioning (a) the color responses of single cells in macaque visual cortex. Specifically, we will investigate the occurrence and organization of color-specific and multiplecolor cells. (b) the spatial and temporal contrast sensitivity of units for both luminance and color modulated light. We plan to study units in optic tract, lateral geniculate and cortex. Responses to more complex waveforms will also be investigated, with emphasis on testing the linearity of the visual system. (c) the orientational selectivity of cortical units and the interactions responsible for producing them.